The Neapolitan War, also known as the Austro-Neapolitan War, was a conflict between the Napoleonic Kingdom of Naples and the Austrian Empire. It started on 15 March 1815, when King Joachim Murat declared war on Austria, and ended on 20 May 1815, with the signing of the Treaty of Casalanza. The war occurred during the Hundred Days between Napoleon's return from exile and before he left Paris to be decisively defeated at the Battle of Waterloo. The war was triggered by a pro-Napoleon uprising in Naples and ended with a decisive Austrian victory at the Battle of Tolentino, after which Bourbon monarch Ferdinand IV was reinstated as King of Naples and Sicily. Many say the declaration of war was a reckless decision by Murat. However, the intervention by Austria caused resentment in Italy, which further spurred the drive towards Italian unification.
Before the French Revolutionary Wars the Kingdom of Naples was ruled by Bourbon King Ferdinand IV. Ferdinand was a natural opponent of Napoleon and was allied with the Third Coalition against him. However, after defeat at the Battle of Austerlitz and the Treaty of Pressburg, Ferdinand was forced to cede Naples to the French in early 1806.
Initially, Napoleon's brother, Joseph Bonaparte, ruled Naples. Then in 1808, Joseph was installed by Napoleon as King of Spain which led to the Peninsular War, and Napoleon installed his brother-in-law, Joachim Murat, as King of Naples.
Murat originally ruled Naples following the same legal and social system used in France, whilst still participating in Napoleon's campaigns. But following the disastrous Battle of Leipzig, Murat abandoned the Grande Armée to try to save his throne. As defeat in the War of the Sixth Coalition loomed, Murat increasingly moved away from a hapless Napoleon, eventually signing a treaty with Austria in January 1814 and joining the Allied side.
But as the Congress of Vienna progressed, Murat's position became less and less secure as there was growing support to restore Ferdinand to the throne. The most vocal of all Murat's opponents was the United Kingdom, which had never recognized Murat's claim to the throne and, moreover, had been guarding Ferdinand in Sicily, ensuring he retained the Sicilian throne.
When Murat was informed of Napoleon's plan to escape from exile in Elba on 1 March 1815, Murat sided with him once more and declared war on Austria as soon as he learned of Napoleon's return to France.
Joachim Murat declared war on Austria on 15 March 1815, five days before Napoleon's return to Paris and the beginning of his Hundred Days. The Austrians were prepared for war after their suspicions were raised when Murat applied for permission weeks earlier to move his troops through Austrian land in order to attack the south of France. Austria had reinforced their armies in Lombardy under the command of Count Heinrich von Bellegarde prior to war being declared.
At the start of the war, Murat reportedly had 82,000 men in his army, including 7,000 cavalry and 90 cannons, although this figure was grossly exaggerated to try to encourage Italians to join his cause. The real number was somewhere in the region of 50,000 men.
Leaving behind a reserve Army of the Interior in case of an invasion from Sicily, he sent his two elite Guard Divisions through the Papal States, forcing the Pope to flee to Genoa. With the remainder of his army, Murat established his headquarters at Ancona and advanced on the road towards Bologna. On 30 March, Murat had arrived in Rimini, where he gave the famous Rimini Proclamation, inciting all Italian nationalists to war.
The Italian population was mostly wary of Habsburg Austria, as they feared the increasing Austrian influence in Italy. Under the terms settled by the Congress of Vienna, direct Austrian rule was imposed on Milan 19 years after Napoleon's invasion. Habsburg princes had also been reinstated in the Grand Duchy of Tuscany and the Duchy of Modena.
Murat was hoping that an Austrian army in Naples would prove too much and that the Italian population would rise up in support of his cause. However, no such general insurrection occurred, as any unrest was quickly quashed by the Austrian authorities, and Murat found few Italians outside Naples who were willing to take up arms and join his cause. Many saw Murat as a man trying to save his crown rather than a beacon of Italian unification.
By now, the number of Austrian troops in Lombardy had swelled to 60,000, and the commander entrusted with the force to confront Murat was Baron Johann Maria Philipp Frimont. The army was originally intended to invade southern France after Napoleon's return, but now had to be diverted to face the approaching Neapolitan army. Frimont moved his headquarters to Piacenza in order to block any potential advance on Milan.
Meanwhile, on the same day that Murat gave the Rimini Proclamation, the Austrian advance guard, under the command of General Frederick Bianchi, was beaten back at an engagement near Cesena. Bianchi retreated towards Modena and took up a defensive line behind the River Panaro, allowing Murat to take Bologna on 3 April.
Murat engaged Bianchi again at the Battle of the Panaro; the Austrians were defeated and driven back. The Austrian vanguard was forced to retreat to Borgoforte, allowing the Neapolitans to advance on Modena.
Following the battle, the division under the command of General Michele Carrascosa immediately occupied Modena, Carpi, and Reggio Emilia, while Murat moved against Ferrara. However, the garrison in Ferrara withstood the best efforts of the Neapolitans to take the citadel, tying up a large number of Neapolitan troops in a costly siege.
On 8 April, Murat attempted to cross the Po River and finally set foot in Austrian-controlled Italy. Murat had received little reinforcement from the Italian populace up to this point, but he hoped he would find more support north of the Po River, which was under direct Austrian rule.
The region had once been part of the Kingdom of Italy, a French client state, and it had been reported that about 40,000 men, mostly veterans of Napoleon's campaigns, were ready to join Murat once he arrived in Milan. He chose a crossing at the town of Occhiobello. It was there that Murat finally engaged with the bulk of the Austrian army under the command of Frimont.
Meanwhile, the two Guard Divisions Murat had sent into the Papal States had passed unmolested into Tuscany, and by 8 April they had occupied Florence, the capital of the Grand Duchy of Tuscany. Ferdinand III fled to Pisa, while the Austrian garrison in Florence, under the command of General Laval Nugent von Westmeath, was forced to retreat to Pistoia, with the Neapolitan army in pursuit.